package com.nowcoder.topic.dp.middle;

import java.util.ArrayList;

/**
 * NC67 汉诺塔问题
 * @author d3y1
 */
public class NC67{
    ArrayList<String> result = new ArrayList<String>();

    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param n int整型
     * @return string字符串ArrayList
     */
    public ArrayList<String> getSolution (int n) {
        // n from left to right
        Hanoi(n, "left", "mid", "right");

        return result;
    }

    /**
     * 递归
     * @param n
     * @param from
     * @param help
     * @param to
     */
    private void Hanoi(int n, String from, String help, String to){
        if(n > 0){
            // step1: n-1 from left to mid
            Hanoi(n-1, from, to, help);
            // step2: 1 from left to right
            result.add("move from "+from+" to "+to);
            // step3: n-1 from mid to right
            Hanoi(n-1, help, from, to);
        }
    }
}